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To all whom it may concern Be it known that I, VANCE P. EDWARDES,

a citizen of the United States, residing at Madison, in the'county ofDane and State of Wisconsin, have invented certain new and usefulImprovements in-the Manufacture' of Cellulose,-0f which the following isa specification. j

This'invention relates to im rovements in the manufacture of cellulosefrom any material containing cellulose and has for its chief object theproduction of a finished, pure product more closely resembling purecellulose in physical andchemical characteristi'cs than any heretoforeproduced.

One object of the iIIVGIItlOIi is to provide j l asatisfactory processfor obtaining. from Wood and vegetable growth a cellulose which can besatisfactorily substituted for cotton in the manufacture ofnitrocellulose, surgical dressings, and other commercial uses. I

The process provides for the treatment of wood pulp, which hasbeengivenapreliml nary treatment by the sulfite process, with asecondary treatment with a weak solution of caustic soda. As a result ofthe treatment the pulp loses about 20% of surplus undesirable matter,the physical characteristics have changed and it is much softer and moreabsorbent and the fiber length has not been,shortened. The resultantpulp can be bleached with a much smaller proportion of bleachingchemical than could the untreated material.

The process may be operated more effectively and at a much lower costthan any known process. The above and other ad vantageous"featureswillbe set forth in the following detailed statement of the process. Incommercial practice, sulfite pulping is carried on bytwo methodsthedirect and indirect. In the first case, wood prepared in a suitablemanner is charged into digesters and a suflicient quantity of acid isrun in. This acid is made up by bringing sulfur dioxid gas into contactwith calcium or magnesium hydroxids, or a mixture of the two, or othersuitable bases and water in sufiicient quantities. The acid compositionmay vary within wide limits and there are a number of standard methodsof preparation in use. It may contain various percentages of such basesas calcium and magnesium or any one base to the total exclu-MANUFACTURED! cELLu'LosE.

cent. total, 6

VANCE r. EDWARDES, or mnmson, WISCONSIN, nssrenon r0 THE UNITED STATESor AMERICA.

Specification of Letters Patent. Patentgdl July 22, 1919, Applicationfiled January 18, 1319. Serial No; 271,891.

be made with acid strength varylng from 3.4 per cent, total sulfurdioxid, 1.7 per cent. free and 1.7 per cent. combined to 7 per per cent.free and 1 per cent. combined;

- The percentage of total S0 is limited by mechanical conditions of theoperation.

For instance, it has been found that when Working with "an acid ofthatcomposition or stronger, it-is impossible, to place the cover. ofthe-digester onas the evolution of gas caused b the contactof the acidwith the heated lining of the digester is suffi cient to generate enoughpressure to blow off the cover. a

The temperatures, pressures, and methods of cooking may also vary, notonly with the acid used but with the judgment of the operator. Forth'equick cook, steam is admitted into the digester and pressures of to 90lbs., with maximum temperatures from 125 C. to 165 C., are carried for 5to 12 hours, with a total cooking time varying from 6' to 14: hours.When the cook is completed, the pulp is. discharged under pressure fromthe digester,'usually into a blow pit where it is drained and washed.

The indirectcook is made much after the same manner, although, as thename implies, no, direct steam is used, the heat being supplied by steamcoils in the digester. The

,wood, in general, is prepared in the same manner as for the direct cookalthough the chips are usually longer. In this process it is quitecommon to rotate the digesters in order to secure better circulation. The acid used here is much weaker than the average practice in the directcook and-will analyze as low as 2.8 per cent. total S0 1-8 per cent.free and 1 per cent. combined. The

time of cooking 1s in the neighborhood of 40 hours, the maximum pressurenot more than 60 lbs. and the maximum temperature about 135 C. It isquite common to steam the wood before admitting acid. Usually the pulpisnot discharged under pressure as in the direct cook. but the pressureisrelieved, the,liquor blown off and then the pulp discharged. There arealso c ombinations of these two processes, in which both direct andindirect steam is used. Var1ations in .the process may be made accordingtothe conditions surrounding the'operation' of the process in the mill.

sion of the other. Satisfactory pulp may For nitration work, chemicalrather than physical qualifications are the desideratwm.

The most important of these is measured by the solubility of'thematerial in a solution of potassium-hydrokid under definite conditions."Unbleached sulfite pulp contains from 1 18-30% and bleached sulfite pulpcontains 30. :Q%, of potassium hydrbxid. soluble matter which-by thealkaline digestion may be reduced to almost any figure desired, de-

pending upon. the treatment employed.-

J After treatment, the pulp is very. readily bleached with theconsumption of far less chemicalsthanj the untreated pulp.

.The practicein commercial sulfite pulping j isto reduce the wood asthoroughly as pos sible, leaving very small percentagesfof undercookedmaterial. In such a case the yield is in the neighborhood of 43%.

This pulp loses 20% .or more'when given the secondary "alkalinetreatment, .thus. re-

' manner is so treated as to, give a uniformly raw cook. By that ismeant that the pulpducing the finalyield in alike proportion,

.and the following modification to the process has been successfullycarried out:

Wood prepared for-pulp1ng in the usual ing process is not-whollycomplete. The

- and temperatures to be used vary with they yield in sucha case willbe: 50% or over and consequently the final yield, after the causticdigestion, greater'than if thoroughly cooked pulp had been-used. Thepulp is separated" from the liquor and is now ready for the secondaryalkalinetreatment of'the invention. The pulp-is cookedin a closed vesselor digester with from 5 to 15 percent. of its weight of caustic soda insolution, the strength of which may vary from {to 2 per cent. and theratio of the weight of liqu or to the pulp-may vary from 6 to 1 and from12 to 1. Various concentrations and O volumes ofsodium hydroxidsolutions may 1 beused. Good results with wood pulp are to 45-.

be had by using a solution of 10% and about 10% concentration, that is,for every 100 grams of pulp,-1O grams of sodium hydroxid made up toIOOOc. e. werev used. Pressures quality and kind'of the pulp used and thequality ofthe pulp desired. The pressure 3 and temperature within theclosed vessel may be controlled as desired. The process may be conductedat a pressure of 1.0 pounds and. with a temperature of about 115 (3..

A satisfactory operation of the process has beenconducted with apressure of 50 pounds -and a-temperature of about 148 C.

of the solution, care must be taken not to .perature of at least 115 C.-

Regardless of the strengthv make the treatment too drastic. In such acase appreciable quantities of cellulose will be dissolved by thecaustic and excessive loss occur. By properly regulating the severity ofthe treatment, this loss can be reduced to a minimum.

g It is known that eflorts have been made to use a subsequent treatmentof caustic soda on a sulfite pulp. All such suggested processes nowknown are chemically wasteful, using many times the amount of chemicalsused in the present process, and are not practicable mechanically.Emphasis is directed to the low chemical consumption of this process,the fact that the sulfite pulp is undercooked, and -to the operation ofthe process under very considerable pressure, for

a relatively short time.

Without any further treatment, paper made from pulp which has beentreated in the manner-indicated inall 0f the foregoing is very soft andabsorbent,.is in a condition suitable for the manufacture ofnitrocellulose, though. possibly a slight bleachin treatment may benecessary, contains no fluff and has other properties which point to itsadaptability as a surgical dressing. In addition to the two usesmentioned, others will suggest themselves, particularly where soft,bsorbent material can be used.

What I claim is 1. The process of producing cellulose which comprisestreating fibrous vegetable material with acid sulfite liquor, separatingthe fibrous material from the liquor, treat-- ing the fibrous materialwith a solution of caustic soda, and subjecting it to' a pressureof atleast ten pounds and to a tem- -2. The process of producing cellulosewhich comprises treating fibrous vegetable material with acid sulfiteliquor, separating the fibrous material from the liquor. treating thefibrous'material with "a solution of'caustic soda of %-2 percent.strength and constituting 5-15 per cent. of the weight of the fibrousmaterial, and subjecting the mixture of fibrous material and causticmaterial to a pressure of at least ten pounds .and a temperature of at.least 115 C. s

3. The process of producing cellulose which comprises treating fibrousVegetable --material with acid sulfite liquor, separat ing the fibrousmaterialfrom the liquor, treating the fibrous material with a solutionof caustic soda, and subjecting it to a pressure of at-lea'st ten poundsand to a tem;

perature of at least 115 'C., said heat and pressure treatment beingmaintained for at least one -hour..

4.- The process of producing cellulose whichicomprises treating fibrousvegetable material with acid su'lfite liquor, separating the fibrousmaterial from the liquor, treating the fi'brous material with a solutionof canstic soda of %-2 per centstrength and con- Stitllti Ilg 5-15percent. of the weight of the" fibrous material, and subjecting themixt'ure of fibrous material andlcaustic' material to a pressure ofatleast ten pounds and a temperature of at least 115 0., saidfiheat andpressure treatment being ,maintaiued for one hour,

5. The process of producing cellulose which comprises treating fibrousvegetable material with vacid'sulfite liquor, separating the fibrousmaterial from the liquor, treating the fibrous material with a solutionof caustic soda constituting; 5-15 per cent. of the weight of thefibrous .materialand subjecting the mixture of fibrous material andcaustic material to a pressure of at least ten pounds and :a temperatureof at least 1 15.C..

.6, The process of producing cellulose which comprises treating fibrousvegetable material with acid sulfite liquor, separating-the fibrousmaterial from the liquor,

treating the fibrous material with a solution of causticsoda andconstituting 5-15 per cent. of the weight ofthe fibrous material, andsubjecting the mixture of fibrous treatment being maintaihed for onehour. 1

material and caustic material to a pressure of at least ten poundsand atemperature of at least 115 C.,sa1d heat and pressure 7. The process ofproducing cellulose which comprises treating fibrous vegetable materialwith acid sulfite liquor, separating the fibrous material'from theliquor,

treating the fibrous material with a solution of caustic soda, andsubjecting it to a pressure of at least fifty pounds and to ate1nperature of atleast 148 C.

.8. The. process of producing cellulose which comprises treating fibrousvegetable material withfacid sulfite liqpor, separating the fibrousmaterial 'from the liquor,

treating the fibrous material with a solution of caustic soda, andsubjecting it to a pressure greater than atmospheric pressure nd to atemperature of at least 115 C.

9. The process of producing cellulose which comprises treating fibrousvegetable material with acid Sulfite liquor, separating'the fibrousmaterial from the liquor,

treating the fibrous material with a solution of caustic alkali, andsubjecting it to a preswhich 11. The process of producing cellulosewhich comprises treating fibrous vegetable material with acid sulfiteliquor and cooking the material so treated to an underdone condition,separating the fibrous material from the liquor, treating'the fibrousmaterial with a solution of caustic soda of -2 per of the weight of thefibrous material, and subjecting the mixture of fibrous material andcaustic material toe-pressure of at least ten pounds and a temperatureof at least 115 C.

12. The process of producing cellulose which comprises treating fibrousvegetable material with acid sulfite liquor and cooking the material sotreated to an underdone condition, separating the fibrous material fromtheliquor, treating the fibrous material with a solution of causticsoda, and subjecting it to a pressure of at least ten pounds and to atemperature ofat least 115 G.,'said heat and pressure treatment being'maintained' for one hour.

13. The process of producing cellulose which comprises treatingfib'rousvegetable material with acid sulfite liquor, and cooking the material sotreated to an underdone condition, separating the fibrous material fromthe liquor, treating the fibrous material with a solution of causticsoda of 4 -2 per cent. strength and constituting 5-15 per cent.

cent. strength and constituting 5-15 per cent.

of the weight of the fibrous material, and

subjecting the mixture of fibrous material and caustic material toa-pressure of at least ten pounds and a temperature of at least r115?..(1, said heat and pressure treatment beingmaintained for one hour.

14. The process of producing cellulose material with acid s,]1lfiteliquor, and cooking the material so treated to an underdone condition,separating thefibrous material from the liquor, treating the fibrousmaterial with a solution of caustic soda constituting 5-15 per cent. ofthe weight of the fibrous materlal and subjecting the mixture of -whichcomprises treating fibrous vegetable fibrous material'andcausticmaterial to a pressure ofi at least ten pounds and a temperatureof at least 0:.

15. The process of 'producing cellulose which comprises treating fibrousvegetable material with acid sulfite liquor, and cooking the material sotreated to an underdone condition, separating the fibrous material fromthe liquorjtreating the fibrousmate'rial with a solution of caustic sodaand constituting 5-15 per cent. of the weight of the fibrous material,and subjecting the mixture of fibrous material and caustic material to apressure of at least tenpounds and a temperature of at least 115 C.,'said heat and pressure treatment being maintained for one hour. 16, Theprocess of producing cellulose comprises treating fibrous vegetablematerialwith acid sulfite liquor, and cookcmaterial withacid sulfiteliquor, and cooking the material so treated to an underdohe condition,separating the fibrous m'aterialfrom the liquor, treating the fibrousmaterial with" a solution of caustic soda, and subjecting it to apressure greater than atmospheric pressure and-to a temperature of atleastl15 C.

181 The process ofproducing" cellulosei' which comprises treatingfibro'usflvegetable materialwith acid sulfite liquor, and cooking thematerial so treated .to anunderdonecondition, separating the fibrousmaterial from the liquor, treating the fibrousmate? rial with a solutionof caustic alkali, and

subjecting it to a pressure greater than atmospheric and toaitemperature of-at-least 115 C. I f. Y I

19. The process of; producing-cellulose which comprises treating fibrousvegetable?- .material withacid sulfite liquor, cooking the materialstopping the cooking action before the pulping action, is complete,separating the'fibro'us material from the liquor, treating tic soda, andsubjecting it to a pressure of at least ten pounds 'and'toa temperatureof at least 115 C.

which comprises treating fibrous egetable material, with acid sulfiteliquor, separating the'fibrous material from the liquor, treating thefibrous material with asolution of treatment being ,maintained for"approximately-'onehourL i I In testimony whereof I affi-x m signature;

y the'fibrous material with a solution of caus- 20. The process ofproducing cellulose caustic soda, and subjecting it tola. pressure v ofat least fi y pounds'and to a temperature of at least 48 0., saidheat'andj pressure v

